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Fors, Carina
Publications (10 of 12) Show all publications
Ahlström, C., Nystrom, M., Holmqvist, K., Fors, C., Sandberg, D., Anund, A., . . . Akerstedt, T. (2013). Fit-for-duty test for estimation of drivers sleepiness level: Eye movements improve the sleep/wake predictor. Transportation Research Part C: Emerging Technologies, 26, 20-32
Open this publication in new window or tab >>Fit-for-duty test for estimation of drivers sleepiness level: Eye movements improve the sleep/wake predictor
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2013 (English)In: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 26, p. 20-32Article in journal (Refereed) Published
Abstract [en]

Driver sleepiness contributes to a considerable proportion of road accidents, and a fit-for-duty test able to measure a drivers sleepiness level might improve traffic safety. The aim of this study was to develop a fit-for-duty test based on eye movement measurements and on the sleep/wake predictor model (SWP, which predicts the sleepiness level) and evaluate the ability to predict severe sleepiness during real road driving. Twenty-four drivers participated in an experimental study which took place partly in the laboratory, where the fit-for-duty data were acquired, and partly on the road, where the drivers sleepiness was assessed. A series of four measurements were conducted over a 24-h period during different stages of sleepiness. Two separate analyses were performed; a variance analysis and a feature selection followed by classification analysis. In the first analysis it was found that the SWP and several eye movement features involving anti-saccades, pro-saccades, smooth pursuit, pupillometry and fixation stability varied significantly with different stages of sleep deprivation. In the second analysis, a feature set was determined based on floating forward selection. The correlation coefficient between a linear combination of the acquired features and subjective sleepiness (Karolinska sleepiness scale, KSS) was found to be R = 0.73 and the correct classification rate of drivers who reached high levels of sleepiness (KSS andgt;= 8) in the subsequent driving session was 82.4% (sensitivity = 80.0%, specificity = 84.2% and AUC = 0.86). Future improvements of a fit-for-duty test should focus on how to account for individual differences and situational/contextual factors in the test, and whether it is possible to maintain high sensitive/specificity with a shorter test that can be used in a real-life environment, e.g. on professional drivers.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
Fit-for-duty test, Eye movements, Driver sleepiness, Field study
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-90685 (URN)10.1016/j.trc.2012.07.008 (DOI)000315421300002 ()
Note

Funding Agencies|Swedish Transport Administration||VINNOVA, the Swedish Governmental Agency for Innovation Systems||

Available from: 2013-04-03 Created: 2013-04-03 Last updated: 2017-12-06
Hallvig, D., Anund, A., Fors, C., Kecklund, G., Karlsson, J. G., Wande, M. & Akerstedt, T. (2013). Sleepy driving on the real road and in the simulator-A comparison. Accident Analysis and Prevention, 50, 44-50
Open this publication in new window or tab >>Sleepy driving on the real road and in the simulator-A comparison
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2013 (English)In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 50, p. 44-50Article in journal (Refereed) Published
Abstract [en]

Sleepiness has been identified as one of the most important factors contributing to road crashes. However, almost all work on the detailed changes in behavior and physiology leading up to sleep related crashes has been carried out in driving simulators. It is not clear, however, to what extent simulator results can be generalized to real driving. This study compared real driving with driving in a high fidelity, moving base, driving simulator with respect to driving performance, sleep related physiology (using electroencephalography and electrooculography) and subjective sleepiness during night and day driving for 10 participants. The real road was emulated in the simulator. The results show that the simulator was associated with higher levels of subjective and physiological sleepiness than real driving. However, both for real and simulated driving, the response to night driving appears to be rather similar for subjective sleepiness and sleep physiology. Lateral variability was more responsive to night driving in the simulator, while real driving at night involved a movement to the left in the lane and a reduction of speed, both of which effects were absent in the simulator. It was concluded that the relative validity of simulators is acceptable for many variables, but that in absolute terms simulators cause higher sleepiness levels than real driving. Thus, generalizations from simulators to real driving must be made with great caution.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
EEG, EOG, KSS, Driving performance, Lateral deviation, Speed, Lateral position, Night, Shift work
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-89811 (URN)10.1016/j.aap.2012.09.033 (DOI)000314191600006 ()
Available from: 2013-03-07 Created: 2013-03-07 Last updated: 2017-12-06
Fors, C., Ahn, H. C. & Wårdell, K. (2008). Online Laser Doppler Measurements of Myocardial Perfusion. In: IFMBE Proceedings 22,2008: . Paper presented at 4th European Conference of the International Federation for Medical and Biological Engineering, ECIFMBE (pp. 1718-1721). Springer Berlin Heidelberg
Open this publication in new window or tab >>Online Laser Doppler Measurements of Myocardial Perfusion
2008 (English)In: IFMBE Proceedings 22,2008, Springer Berlin Heidelberg , 2008, p. 1718-1721Conference paper, Published paper (Refereed)
Abstract [en]

Laser Doppler perfusion monitoring is a suitable method for microvascular blood perfusion measurements. When used on a moving tissue or organ, the Doppler signal arising from the moving blood cells may be distorted. ECG triggering of the laser Doppler signal can be used for reducing the influence from movements during measurements on the beating heart. The aim of this study was to determine the most appropriate triggering intervals during the cardiac cycle for online measurements. Recordings from thirteen coronary artery bypass graft (CABG) patients were included in the study. During surgery, the fibre-optic probe was passed through the chest wall and sutured to the left anterior ventricular wall with the probe tip inserted 3–5 mm into the myocardium. After the patient arrived at the intensive care unit a second measurement was initiated and lasted for about two hours. Before the probe was removed a third measurement was performed for about 5 minutes the following morning. A total of 97 data sequences were analysed and the intervals of low and stable perfusion signal were compared to the positions of the T and P peaks in the ECG.

It was found that the most appropriate time intervals were in late systole at the T peak [−3, 9] ms and just before the P peak [−28, -10] ms in late diastole. However, the position of these intervals may vary between individuals, because of e.g., abnormal cardiac motion. With the use of the appropriate interval online measurement of the myocardial perfusion on a beating heart appears possible.

Place, publisher, year, edition, pages
Springer Berlin Heidelberg, 2008
Series
IFMBE Proceedings, ISSN 1680-0737 ; 22
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-44433 (URN)10.1007/978-3-540-89208-3_409 (DOI)76617 (Local ID)978-3-540-89207-6 (ISBN)978-3-540-89208-3 (ISBN)76617 (Archive number)76617 (OAI)
Conference
4th European Conference of the International Federation for Medical and Biological Engineering, ECIFMBE
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-02-16Bibliographically approved
Wårdell, K., Fors, C., Antonsson, J. & Eriksson, O. (2007). A laser Doppler system for intracerebral measurements during stereotactic neurosurgery. In: Engineering in Medicine and Biology Society, 2007. EMBS 2007: . Paper presented at 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBS 2007), 22-26 August 2007, Lyon, France (pp. 4083-4086). IEEE
Open this publication in new window or tab >>A laser Doppler system for intracerebral measurements during stereotactic neurosurgery
2007 (English)In: Engineering in Medicine and Biology Society, 2007. EMBS 2007, IEEE , 2007, p. 4083-4086Conference paper, Published paper (Refereed)
Abstract [en]

A laser Doppler system for intracerebral measurements during stereotactic and functional neurosurgery is presented. The system comprises a laser Doppler perfusion monitor, an optical probe adapted for the Leksellreg stereotactic system and a personal computer with software for acquisition, data analysis and presentation. The software makes it possible to present both the perfusion and the total backscattered light intensity (TLI) in real-time. During intracerebral measurements, the perfusion signal records the tissue's microcirculation whereas the TLI signal may be used to distinguish between grey and white matter. Evaluation of the system has been done during stereotactic neurosurgery in relation to implantation of deep brain stimulation electrodes. Measurements were made along trajectories towards targets in the deep brain structure as well as in pre-calculated target areas. The measurements show that the system has a potential to be used for intracerebral guidance but further evaluation of the technique is needed.

Place, publisher, year, edition, pages
IEEE, 2007
Series
IEEE Engineering in Medicine and Biology Society. Conference Proceedings, ISSN 1557-170X
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-38409 (URN)10.1109/IEMBS.2007.4353231 (DOI)44245 (Local ID)9781424407873 (ISBN)9781424407880 (ISBN)44245 (Archive number)44245 (OAI)
Conference
29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBS 2007), 22-26 August 2007, Lyon, France
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-02-17Bibliographically approved
Fors, C., Casimir Ahn, H. & Wårdell, K. (2007). Determination of appropriate times during the cardiac cycle for online laser Doppler measurements of myocardial perfusion.
Open this publication in new window or tab >>Determination of appropriate times during the cardiac cycle for online laser Doppler measurements of myocardial perfusion
2007 (English)Article in journal (Refereed) Submitted
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14614 (URN)
Available from: 2007-08-27 Created: 2007-08-27 Last updated: 2017-02-16Bibliographically approved
Fors, C. (2007). Evaluation of a Laser Doppler System for Myocardial Perfusion Monitoring. (Licentiate dissertation). : Institutionen för medicinsk teknik
Open this publication in new window or tab >>Evaluation of a Laser Doppler System for Myocardial Perfusion Monitoring
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Coronary artery bypass graft (CABG) surgery is a common treatment for patients with coronary artery disease. A potential complication of CABG is myocardial ischemia or infarction. In this thesis, a method - based on laser Doppler flowmetry (LDF) - for detection of intra- and postoperative ischemia by myocardial perfusion monitoring is evaluated.

LDF is sensitive to motion artifacts. In previous studies, a method for reduction of motion artifacts when measuring on the beating heart has been developed. By using the ECG as a reference, the perfusion signal is measured in intervals during the cardiac cycle where the cardiac motion is at a minimum, thus minimizing the artifacts in the perfusion signal.

The aim of this thesis was to investigate the possibilities to use the ECG-triggered laser Doppler system for continuous monitoring of myocardial perfusion in humans during and after CABG surgery. Two studies were performed. In the first study, changes in myocardial perfusion during CABG surgery were investigated (n = 13), while the second study focused on postoperative measurements (n = 13). In addition, an ECG-triggering method was implemented and evaluated.

It was found that the large variations in myocardial perfusion during CABG surgery could be monitored with the ECG-triggered laser Doppler system. Furthermore, a perfusion signal of good quality could be registered postoperatively from the closed chest in ten out of thirteen patients. In eight out of ten patients, a proper signal was obtained also the following morning, i.e., about 20 hours after probe insertion. The results show that respiration and blood pressure can have an influence on the perfusion signal.

In conclusion, the results indicate that the method is able to detect fluctuations in myocardial perfusion under favourable circumstances. However, high heart rate, abnormal cardiac motion, improper probe attachment and limitations in the ECG-triggering method may result in variations in the perfusion signal that are not related to tissue perfusion.

Abstract [sv]

Varje år utförs omkring 4500 kranskärlsoperationer i Sverige. En allvarlig komplikation som kan uppstå efter operationen är otillräcklig blodförsörjning till hjärtmuskeln. Den här licentiatavhandlingen handlar om utveckling och utvärdering av en metod, baserad på laserdopplerteknik, för att kunna upptäcka nedsatt blodperfusion i hjärtmuskeln på ett tidigt stadium.

Laserdopplertekniken är känslig för rörelsestörningar. I tidigare studier har en metod för reducering av rörelsestörningar vid mätning på slående hjärta tagits fram. Med EKG:t som referens mäts blodperfusionen i de faser under hjärtcykeln då hjärtats rörelse är som minst, vilket minskar bidraget av rörelsestörningar i blodperfusionssignalen.

I den här avhandlingen undersöks om metoden kan användas för kontinuerlig övervakning av hjärtmuskelns blodperfusion på patienter under och efter hjärtoperationer. Två studier har genomförts: en där hjärtmuskelns perfusion mättes i olika faser under kranskärlsoperationer och en där mätproben lades in i hjärtmuskeln under operationen och mätningar gjordes under det första dygnet efter operationen.

Det visade sig vara möjligt att följa förändringar i hjärtmuskelns blodperfusion under operation. Det var även möjligt att registrera en perfusionssignal av god kvalitet efter operationen då bröstkorgen var stängd. Hos åtta av tio patienter erhölls en bra signal även morgonen efter operationen, dvs. ca 20 timmar efter att proben lades in. Resultaten visar också att andning och blodtryck kan ha en påverkan på blodperfusionssignalen.

Slutsatsen av arbetet är att det går att se variationer i hjärtmuskelns blodperfusion med EKG-triggad laserdoppler under vissa förutsättningar. Signalen är dock i många fall svårtolkad på grund av att t ex hög hjärtfrekvens, onormal hjärtväggsrörelse eller ändrad probposition sannolikt kan ge variationer i perfusionssignalen som inte är relaterade till blodflödesförändringar.

Place, publisher, year, edition, pages
Institutionen för medicinsk teknik, 2007. p. 53
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1326
Keywords
Laser Doppler perfusion monitoring, myocardial microcirculation, coronary artery bypass graft
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-9584 (URN)978-91-85831-16-6 (ISBN)
Presentation
2007-09-17, IMT1, Institutionen för medicinsk teknik, Universitetssjukhuset, Linköping, 13:15 (English)
Opponent
Supervisors
Note
Report code: LIU-TEK-LIC-2007:35.Available from: 2007-08-27 Created: 2007-08-27 Last updated: 2016-05-04
Fors, C., Ahn, H. C. & Wårdell, K. (2006). Analysis of Breathing-related Variations in ECG-triggered Laser Doppler Perfusion Signals Measured on the Beating Heart during Surgery. In: IEEE 2006,2006: (pp. 181-184).
Open this publication in new window or tab >>Analysis of Breathing-related Variations in ECG-triggered Laser Doppler Perfusion Signals Measured on the Beating Heart during Surgery
2006 (English)In: IEEE 2006,2006, 2006, p. 181-184Conference paper, Published paper (Refereed)
Abstract [en]

    

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-36207 (URN)30545 (Local ID)30545 (Archive number)30545 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-02-17Bibliographically approved
Fors, C., Casimir Ahn, H. & Wårdell, K. (2006). Analysis of breathing-related variations in ECG-triggered laser Doppler perfusion signals measured on the beating heart during surgery. Computers in cardiology, 33, 181-184
Open this publication in new window or tab >>Analysis of breathing-related variations in ECG-triggered laser Doppler perfusion signals measured on the beating heart during surgery
2006 (English)In: Computers in cardiology, ISSN 0276-6574, Vol. 33, p. 181-184Article in journal (Refereed) Published
Abstract [en]

Laser Doppler perfusion monitoring (LDPM) is a

method to assess microvascular perfusion. A modified,

ECG-triggered LDPM system has been developed to

measure myocardial perfusion with minimum influence

from heart motion. With this method, one systolic (PLS)

and one diastolic (PLD) perfusion value is obtained.

The aim of this study was to analyse breathing-related

variations in PLS and PLD measured during open-heart

surgery. The phase delays between PLS, PLD, mean

arterial blood pressure (MAP), heart rate and, indirectly,

the respiration were determined.

MAP tended to be in phase with or precede the

variations in PLD, i.e., PLD was at a maximum at the end

of inspiration or at the beginning of expiration. No clear

relation between PLS and any of the other signals could

be found.

National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-14613 (URN)2-s2.0-50149103402 (Scopus ID)
Available from: 2007-08-27 Created: 2007-08-27 Last updated: 2017-12-13Bibliographically approved
Fors, C., Ahn, H. C. & Wårdell, K. (2006). Postoperativa mätningar av myokardperfusion med EKG-triggad laser Doppler. In: Medicinteknikdagarna 2006,2006: .
Open this publication in new window or tab >>Postoperativa mätningar av myokardperfusion med EKG-triggad laser Doppler
2006 (Swedish)In: Medicinteknikdagarna 2006,2006, 2006Conference paper, Published paper (Other academic)
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-36213 (URN)30568 (Local ID)30568 (Archive number)30568 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-02-17Bibliographically approved
Fors, C., Karlsson, D. M., Ahn, H. C. & Wårdell, K. (2005). Myocardial perfusion assessment using an ECG triggered laser doppler technique. In: 13th Nordic Baltic Conference Biomedical Engineering and Medical Physics,2005: (pp. 83-84). Umeå: IFMBE
Open this publication in new window or tab >>Myocardial perfusion assessment using an ECG triggered laser doppler technique
2005 (English)In: 13th Nordic Baltic Conference Biomedical Engineering and Medical Physics,2005, Umeå: IFMBE , 2005, p. 83-84Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Umeå: IFMBE, 2005
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-28744 (URN)13918 (Local ID)13918 (Archive number)13918 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-02-21Bibliographically approved
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